Creating aligned and oriented fiber reinforced polymer composites

ABSTRACT

A method includes providing a reservoir of randomly oriented fibers in a solution, dispensing the solution of randomly oriented fibers through a nozzle having an orientation component onto a porous substrate as a solution of aligned fibers, and immobilizing the fibers to form a fiber pre-form. A system includes a porous substrate, a deposition nozzle, a reservoir of randomly oriented fibers in solution connected to the deposition nozzle, the deposition nozzle position adjacent the porous substrate and connected to the reservoir, the nozzle to receive the randomly oriented fibers and output aligned fibers, and a vacuum connected to the porous substrate to remove fluid from the porous substrate as the deposition nozzle deposits the aligned fibers on the porous substrate to produce a fiber pre-form having aligned fibers.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of and claims priority to and thebenefit of U.S. patent application Ser. No. 14/793,193 filed Jul. 7,2015, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The disclosure here relates to fiber composite sheets, more particularlyto aligned and arbitrarily oriented fiber reinforced fiber compositesheets.

BACKGROUND

Manufacturing processes may employ fiber preforms. The preformstypically consist of sheets or mats of fibers. The mats are shaped intodesired forms or inserted into molds as a matrix. Polymer materials arethen infused into the matrix and the desired article is formed. Thearticle is then hardened and removed from the mold.

Formation of the fiber preforms typically involves a complicated,expensive process with expensive equipment. One challenge lies inattempts to orient the fibers in a desired direction for betterstrength. Advances in printing technology may hold the answer toreducing the costs and complexity of the process while also allowing forbetter alignment of the fibers, but to date no such approach exists.

SUMMARY

According to aspects illustrated here, there is provided a methodincluding providing a reservoir of randomly oriented fibers in asolution, dispensing the solution of randomly oriented fibers through anozzle having an orientation component onto a porous substrate as asolution of aligned fibers, and immobilizing the fibers to form a fiberpre-form.

According to aspects illustrated here, there is provided a systemincluding a porous substrate, a deposition nozzle, a reservoir ofrandomly oriented fibers in solution connected to the deposition nozzle,the deposition nozzle position adjacent the porous substrate andconnected to the reservoir, the nozzle to receive the randomly orientedfibers and output aligned fibers, and a vacuum connected to the poroussubstrate to remove fluid from the porous substrate as the depositionnozzle deposits the aligned fibers on the porous substrate to produce afiber pre-form having aligned fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flowchart of an embodiment of a method to produce a fiberreinforced composite from a preform with oriented fibers.

FIG. 2 show an embodiment of a system to produce a fiber reinforcedcomposite from a preform with oriented fibers.

FIG. 3 shows an embodiment of a four-roll mill.

FIG. 4 shows an embodiment of a fiber orientation and alignment headwith a two-roll mill.

FIG. 5 shows a representation of an orthogonal extensional flow.

FIG. 6 shows an alternative representation of an orthogonal extensionalflow.

FIGS. 7-9 show embodiments of changing angles of fibers from anorientation and alignment head.

FIG. 10 shows an alternative embodiment of a fiber orientation andalignment head with recycling flow.

FIGS. 11-12 show an embodiment of fiber immobilization.

FIG. 13 shows an embodiment of a method to infiltrate a fiber preformwith a matrix.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIGS. 1 and 2 show an embodiment of a system and method to createoriented fiber preforms and then subsequently using that preform toproduce a fiber reinforced composite. The discussion of FIG. 1 will bein conjunction with other drawings to provide information about theembodiments and variations in the system.

At an initial part of the process, a fiber suspension in a fluid iscreated at 10. The suspension may consist of a low-volume fraction of afibers dispersed in a solution. In one embodiment, the solution mayconsist of a Newtonian fluid. In one embodiment, the solution mayinclude a binder. In the system diagram of FIG. 2, the system 30includes a reservoir 32 to hold the suspension.

At 12, a fiber orientation and alignment head, show at 34 in FIG. 2,dispenses the fiber suspension onto a substrate of some sort. In oneembodiment, shown in FIG. 2, the substrate 38 is a perforated and/orporous substrate held by a fixture 36. The substrate may be mounted orotherwise connected to an aspiration system such as a vacuum. Anaspiration device such as vacuum 40 removes extra fluid from thesuspension to leave the fibers behind. This results in a high fractionalcomposition fiber mat.

Once the solution has been dispensed to sufficiently build up a preformmat, or during dispensing, the preform undergoes some sort ofimmobilization or adhering process at 14 to fix the fibers in place andsolidify or semi-solidify the preform. The immobilization may involve abinder in the solution, as discussed above, as the solution is removed,the binder stays behind and fixes the fibers in place. As will bediscussed in more detail, an adhesive or binder may be sprayed onto thepreform.

The embodiments here are directed to the formation of the preform withoriented fibers formed using a unique fiber orientation head. Oncemanufactured, this preform may receive a matrix of polymer/resin to forma fiber reinforced composite. For completeness, this discussion sets outembodiments of how to perform an infiltration of the matrix into thepreform, with the understanding that this process is optional and maytake many different forms.

The preform receives the matrix at 16 in FIG. 1. The matrix may consistof many different materials, including but not limited to, various typesof polymers such as resins, polyurethane compounds, etc. and may be inliquid form or take the form of sheets of thermoplastic or othermoldable materials. Many different types of materials can be used. Ingeneral, any material that is used for Resin Transfer Molding (RTM) orResin Infusion Molding (RIM) could be used. They key is to adjust theviscosity and curing properties to make them compatible with theinfusion process, and this would depend on the particular pre-form thatis made. Typical viscosities are in the range 50-1000 centipose. CommonRTM and RIM materials include: unsaturated polyesters, vinyl esters,epoxies, polyimides, phenolics, etc. It may be possible to usethermoplastics if adjustments are made for their high viscosity. Theprocess needs to control the temperature well enough to achieve areasonably low viscosity. Common thermoplastics include: polypropylene,nylon, polycarbonate, poly-ethylene terephthalate (PET),acrylonitrile-butadiene-styrene (ABS), etc. In the example of FIG. 2,the matrix is fed into the preform as a liquid through the feedmechanism 44.

The infiltration process results in a wet matrix contained by the fiberpreform. This structure requires setting to form a finished reinforcedfiber composite. The setting operation may involve the application ofheat and/or pressure, then a cooling process to solidify the matrix withthe preform at 18 in FIG. 1. The post-processing will depend on thematerial that is infused. At 20 in FIG. 1, this results in a fiberreinforced composite 42 in FIG. 2.

Several aspects of this overall discussion have unique features. Onesuch feature is the fiber orientation and alignment head 34 shown inFIG. 2. The fiber orientation head creates an extensional flow, andextensional flows are ideal for alignment of fibers in a suspension.FIG. 3 shows an example of a mechanical four roll mill. The mechanicalfour roll mill has two inlets 41 and 43. The 4 rolls of the mill counterrotate, pushing the liquids out the outlets 45 and 47. This type ofextensional flow from the outlets causes fibers in the suspension toalign.

FIG. 4 shows one embodiment of a fiber alignment head, which may bereferred to as a fiber alignment and orientation head. The alignmenthead has a housing 35 that contains the orientation component, discussedin more detail later. In FIG. 4, the housing 35 has a rotating ring 48that can control the angle of the alignment of the fibers as they exitthe head. In this embodiment, the housing contains a 2-roll mill. Thesuspension with the fibers flows from the bottom of the housing as shownin the drawing, into the 2-roll mill. The motion of the rollers causesthe fibers to align as they exit the outlet 48.

The flows may be better understood looking at the flow diagram of FIG.5. The housing 34 has an inlet flow 52 that narrows into a path 54between rolls and then exits the print head as an aligned flow. In theembodiment of a rolling mill, the rollers create a splaying flow asshown in FIG. 6. The rollers cause the fibers to align between then inthe region 54 and then exit the mill in a flow 60.

As mentioned above the head may rotate or may have a rotational ring 48at the outlet. The rotation can alter the angle for the fibers as theyexit the head. FIGS. 7-9 show different possibilities. In FIG. 7, thefibers are aligned horizontally relative to the picture. As the rotationrate of the head or ring increases, the exit angle for the fiberchanges. FIG. 8 shows a first exit angle that comes from a firstrotation rate, and FIG. 9 shows a second exit angle that comes from asecond rotation rate. Different applications may have different preformswith different angles and different structural aspects. The ability torotate the output allows for better control of the fiber orientation.

In an alternative embodiment to the rollers within the housing, thehousing could have a structure within it that creates this splayingflow. FIG. 10 shows an alternative housing 70. The housing has acylindrical portion 72, which narrows down into the output portion 74.As the cylindrical portion tapers down to the output portion 74, thedimensions of the output portion get larger or ‘wider’ in the directionof the flows shown by the arrow, but get smaller orthogonal to the flowdirection. In the example shown, the resulting output portion has alarger dimension left to right on the page than the cylindrical portion,but is much narrower going into and out of the page. This results in theoutput portion of the housing being not much wider than the width of theslit 76.

FIG. 10 shows the details of the inside of the housing of thisembodiment as well as the addition of a recycling flow. As the materialenters the head from the reservoir 82 in the flow direction 52, theinlet narrows to a contraction 78. The contraction 78 forces the fiberswithin the solution to begin to align parallel to the flow axis. Thisguarantees that all fibers exit in the center of the nozzle and have thesame starting orientation before processing to the expansion portion 74.The contraction is followed by the expansion outlet portion 74. Theoutlet portion widens in one direction over the contraction 78, butnarrows in a dimension orthogonal to the widening direction. This causesalignment orthogonal to the flow axis.

This may be sufficient to cause the fibers to align. As an enhancement,the alignment head may have a recycling flow outlet 84 that appliesnegative pressure to pull the flow in the direction shown by the arrows86 and 88. This will be referred to the recycling or secondary flow. Themain flow moves out of the nozzle in the direction of the arrow 80. Therecycling flow assists in the alignment of the fibers as they exit thehead. This enhances the splaying flow discussed above.

Regardless of the embodiment of the fiber orientation head used, thepreform may need to undergo further processing prior to the infiltrationwith the matrix. During fiber deposition, vacuum pressure will serve tocompress and immobilize the deposited fibers and remove the carrierfluid. In addition, the fibers may undergo further immobilization. Thesolution may include a binder that holds the fibers in place when thefluid is removed. Alternatively, the fiber preform may be sprayed orotherwise coated at least partially with a binder solution. The bindermay facilitate handling of the fiber perform for the next processingstep. It may also improve the thermoplastic interface quality of thepreform when it is infiltrated with the matrix.

FIG. 11 shows a side view of the fiber preform 39 as it undergoesdeposition with an applied vacuum. The substrate 38 is porous, whichallows the vacuum to act on the preform. As shown in FIG. 12, sprayheads such as 90 dispense the binder solution onto the preform. Thebinder may need to undergo a further setting process such as drying orapplication of heat.

As mentioned above, once the preform with the oriented fibers iscompleted, it may be infiltrated with a matrix. One embodiment of such aprocess is shown in FIG. 13. The fiber preform 39 may be coated orinfiltrated with a molten polymer or resin 94 using an applicator 92such as a curtain, slot, roll coater, etc. The matrix may solidifymerely by allowing it to cool and/or dry. Alternatively, the matrix mayrequire the application of heat and pressure as shown in FIG. 13,resulting in the fiber reinforced composite 42.

In this manner, a unique nozzle allows for orientation of fibers in asolution to create a fiber preform. The preform may have fibersorientated according to the form needed. After infiltration of thematrix, the resulting fiber reinforced composite material or shape hassuperior strength and the nozzle enables relatively inexpensive,relatively simple manufacturing.

It will be appreciated that several of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations, or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

What is claimed is:
 1. A method, comprising: providing a reservoir ofrandomly oriented fibers in a solution; dispensing the solution ofrandomly oriented fibers through a nozzle having an orientationcomponent onto a porous substrate as a solution of aligned fibers; andimmobilizing the fibers to form a fiber pre-form.
 2. The method of claim1, further comprising infiltrating the fiber pre-form with a matrix. 3.The method of claim 2, further comprising forming the fiber pre-forminto a predefined shape prior to infiltrating.
 4. The method of claim 1,applying heat to lower the viscosity of the solution.
 5. The method ofclaim 2, further comprising setting the matrix.
 6. The method of claim1, wherein immobilizing the fibers comprises applying vacuum pressure tothe porous substrate during the dispensing.
 7. The method of claim 1,wherein immobilizing the fibers comprises applying a binder suspensionto the porous substrate after the dispensing.
 8. A system, comprising: aporous substrate; a deposition nozzle; a reservoir of randomly orientedfibers in solution connected to the deposition nozzle; the depositionnozzle position adjacent the porous substrate and connected to thereservoir, the nozzle to receive the randomly oriented fibers and outputaligned fibers: and a vacuum connected to the porous substrate to removefluid from the porous substrate as the deposition nozzle deposits thealigned fibers on the porous substrate to produce a fiber pre-formhaving aligned fibers.
 9. The system of claim 8, further comprising areservoir of matrix material positioned such that the matrix materialcan infuse the fiber pre-form.
 10. The system of claim 9, furthercomprising a heat source.
 11. The system of claim 9, further comprisinga pressure source to apply pressure to the matrix material to assistwith infiltration of the matrix and set the matrix material into thefiber pre-form.
 12. The system of claim 8, wherein the deposition nozzlefurther comprises: a housing; an inlet into the housing arranged toreceive a solution carrying randomly oriented fibers; an orientationcomponent within the housing, the orientation component positioned toreceive the solution from the inlet and operate to produce alignedfibers in a predetermined, single direction; and an outlet on thehousing arranged to receive the fibers and deposit them on a substrate.